Supporting objects on slippery surfaces is usually only reliable if the object applies a vertically downward force on the slippery surface. For example, placement of tall objects, such as poles, boards, and ladders, are often positioned so they lean against a tall stable object, such as a wall or roof. This puts a significant lateral or horizontal force on the foot of the object supported on the surface. If the surface under the object is smooth, the foot of the object tends to slip away from the object it is leaning against.
In particular, falling from ladders is one of the major safety issues in the workplace and particularly in construction. Ideally, ladders are placed on firm, level surfaces that provide a reliable grip for the feet of the ladders. Ladders often get set up on any surface that exists, regardless of whether it is smooth, textured, uneven, or slippery. For example, ladders often get set up on relatively smooth surfaces like waxed floors or artificial decks and don't have safety feet designed to keep them from slipping out from under the worker. Safety experts recommend that If the worker is not able to set up his or her ladder on a firm, level surface, the worker shouldn't set up the ladder at all. However, the exigencies of work and the over-confidence of the worker often leads to ladders being used in less than the safest conditions. Intermediary support bases exist that improve the stability of ladders on various surfaces, but they may still be subject to slippage on particularly smooth, wet, or other slippery surfaces.